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    <script>
        //ES6 允许给函数参数赋值初始值
        //1.形参初始值  具有默认值的参数  一般位置要靠后(潜规则)
        function add(a, b, c = 2) { //此处给形参设置默认值
            return a + b + c;
        };
        let result = add(1, 2);
        console.log(result);
        //当没有第三个实参传入时,可以在形参中设置默认值,否则就是NaN

        //2.与结构赋值结合
        function connect({
            host,
            username,
            password,
            port
        }) {
            console.log(host);
            console.log(username);
            console.log(password);
            console.log(port);
        }
        connect({
            host: '',
            username: 'root',
            password: 'root',
            port: 3306,
        });
    </script>
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